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UNITED STATES PATENT oFFIonu JOSEPH H. WEEKS, OE RUTLEDGE, PENNSYLVANIA, ASSIGNOR TO JACKSON 8. WEEKS, OF DELAWARE COUNTY, PENNSYLVANIA, AND RAYMOND M. WEEKS, OF PHILADEL- PHIA, PENNSYLVANIA, TRUSTEES.

COMPOSITION FOR ELECTROLYTES FOR ELECTRICAL ETCHING.

No Drawing.

To all whom it may concern:

Be it known that I, JOSEPH H. WEEKS, a citizen of the United States, residing at Rutledge, in the county of Delaware and State of Pennsylvania, have invented certain new and useful Improvements in Composition for Electrolytes for Electrical. Etching, of which the following is a specification.

My invention has for its object the production of an improved electrolyte for use in electrical etching of metals.

The general subject matter to which this invention relates is discussed in my prior 1 applications, Serial Numbers 88,362, 108,232,

The electrolyte which I and 119,548, filed respectively April 1, 1916, July 8, 1916, and September 11, 1916. In the first of said applications, I have disclosed a method, apparatus and certain compositions for electrolytes intended to be used therein; in the second application, I have described and claimed a process and composition, and in the third application, I have described and claimed certain improved apparatus. shall hereinafter set forth is adapted for use in the aforesaid processes, and with the aforesaid apparatus, although it is not necessarily limited thereto, and may be employed in other connections, and for other metals or alloys of metals than those therein specifically described.

In the prior applications referred to, I have set forth a method of etching plates in which a resistant image is produced on a plate, either by means of ink or powder, which is well known in the art, or by means of a special gelatin albumen enamel of my own invention. The plate so prepared is suspended in a suitable bath or solution and connected so as to form the anode terminal of a circuit supplied with current of suitable voltage to produce the desired amperage or volume of current flow per unit area of the anode. The cathode terminal, which is also immersed in the bath or solution, may be of various types and of various materials. In my application I have described carbon cathodes, and have set forth means for keeping the surface of the plate clean so that it shall be completely and uniformly exposed Specification of Letters Patent.

.must be properly regulated, and this to a much greater degree of accuracy and uniformity than is necessary in the art of deposition.

In my experimental work, which has extended over a considerable period, and in the course of which the present invention and the others hereinbefore referred to have been produced, I have found that the composition of the electrolyte plays a very considerable part, not only in the regulation of the action on the plate, but in the uniformity of such action, and in maintaining said uniformity for any appreciable period of time.

Without going into detail at this time, into the chemical reactions or the steps in transference of the metals, which take place with any particular composition, I may say generally that I have found it necessary to provide a solution which shall have, first, the proper conductivity; second, a capacity for absorbing and transferring the electrically displaced metal from the late without soon becoming saturated or c ogged; third, no tendency to foul or coat or form bubbles or spots .upon the plate, which would impede the free passage of the current and thereby mar the engraving; fourth, no tendency, or a reduced tendency, to foul and form sludge upon the cathode surface in such manner that it cannot be readily removed; and fifth, such elements and such a balance of forces and properties that its efiiciency will remain unimpaired for a considerable period of time, and use.

The solution which I shall hereinafter set forth, and which has for its principal active element a tartrate or tartrates. either alone Patented Sept. 2, 1919.

Application filed April 80, 1917. Serial No. 165,475.

or in combination with certain other substances, meets those conditions, and has enabled me, by actual test, to produce as good resultswith the last plate of a long series, as

with the first one, for example the same depth 1 the metals specified in my prior applications above referred to, and many others. The metals most commonly employed in the engraving art are copper, brass,.ste'el, and zinc, and the plates are employed for printing,

stamping, and for other purposes. In addition to the engraving of steel printing plates both in relief and intaglio, the manufacture of steel dies and plates for stamping I metals is, in itself, very important, and by my process, and with my' solutions, I can produce such dies and plates in much less time, and with much less expense, than where they are cut by hand according to the practice prior to this invention. Where the .plates are to be employed for printing, my

invention is specially important at the present time, because of the scarcity of high grade paper, and the necessity for having perfect printing plates in order to produce satisfactory results on the cheap grade of paper now commonly employed, because of such scarcity. t v

Electrolytes are prepared, for the greatest efliciency and economy, for the particular metals. to be etched. Wherever practicable, a combination is used in which the plate to be etched is kept clean without wiping. This is especially requisite in very delicate work,

as frequent wiping would tend to injure the material of the image. In coarse work, this is relatively immaterial, and an electrolyte involving wiping of the plate may easily be used, and would be used where it is cheaper to prepare, or produces a speedier act-ion.

The cleanliness of the cathode is next preferable as involving less labor in keeping clean, or as rendering that portion of my apparatus having movable brushes unnecessary, with a consequent saving in power used thereby. For the reasons stated, some of my formulae do not give both a clean cathode and a clean anode.

' The various use of tartrates, sulfates, ni-

" trates, chlorids and chromates, with or without acids, is in some instances to'secure anode or cathode plate cleanhness or both,

aeiae ai and to obtain electrolytes which shall form the ,best chemical. combinations in themselves and with the anode, shall have the longest life, and produce the smoothest etching, z'. e., to avoid rough grainy etching on either the sides of the lines or the bottom,

and -further, to secure a desirable speed which will admit of commercial etching of p the various metals with practically the same electric current density. The'value' of this last is obvious, particularly where one dynamo or battery set is employed to supply current for the etching of diflerent metals in separate tanks without the employment of resistance.

An acid condition is desirable in all elece trolytes to give stability, to the same and to increase theconductivity. If 'theconstituent. salts do not renderthe electrolyte acid or suficiently acid for these purposes, an,

acid should beadded. Some excellent elec trolytes would promptly separate under I electrolysis and promptly become useless were it not for the addition of the 'acid. Even if this does not occur the life of the electrolyte is shorter without acid and its con-,,

ductivity. less. Further in many cases the presence of an acid prevents precipitations" in the electrolyte or on thecathode vor on the anode or tions.

performs two or all of thesefunc- In some combinations where the ordinary acids do not keep the cathode or the anode clean or preventprecipitations in the bath, this may in some instances be partly or wholly accomplished by the addition ofa chromium salt, or by what is generally I termed chromic acid (usually potassium dichromate solution acted upon by sulfuric.

acid), although the action herein stated does not depend on the sulfuric acid in the chromic acid as that might independently be present in or added to'the electrolyte under the head of acids. The chromium salts are also employed on account of their.-tendency vto produce a smooth surface in the anode where it is found that ordinarily the surface is rough, smoothness of the anode being usually a desirable feature.

Specifically stated, the solution to be claimed herein-consists essentially of one or' more of the tartrates of antimony, ammonium, barium, boron, calcium,-cadmium, iron,

lithium, magnesium, potassium, sodium and strontium.

While the essence of the invention isthe. use of a suitable tartrate, I may and do employ more than one, in combination, whenrequired, but it is obvious that only those which will properly mix or combine can vbe simultaneously employed.

With the tartrates, I may combine asul fate, a nitrate, a chlorid or a chromium salt,

. or any combination thereof, with or without the addition of an acid. I may also employ,

as an additional element, a small quantity of a perchlori'd, such as the perchlorid of iron, containing an excess of acid. This may be used in lieu of one or more of the foregoing tartrates, and in such case, no other acid is usually necessary. The rincipal function of the separate acid, if a ded, is to increase the conductivity and prevent decrease in current density and tends in most cases to keep the face of the plate clean and to prevent disintegration 0 the solution.

As an example of a solution in which a tartrate and an acid are employed, I may give the following:

Ammonium tartrate 240 grains. \Vater 4 oz. Sulfuric acid 0. P oz.

As an example of a solution in which a tartrate, a sulfate, a nitrate, a chlorid and an acid are employed, I may give the following:

Iron sulfate 30 grains.

Iron nitrate 60 grains. Potassium tartrate 60 grains. Water 3 oz. Ammonium chlorid solution in water to 15 Baum 1 oz, Sulfuric acid oz.

As an example of a tartrate, and an acid together with a chromium salt, I may give the following:

As an example of a tartrate, a chlorid and an acid, I may give the following:

As an example of a tartrate, a sulfate and one or more acids, I may give the following:

Ammonium tartrate 80 grains.

Water 2 oz. Ammonium sulfate"; 120 grains. Water 2 oz. Sulfuric acid 0.1 oz. Ammonium tartrate 120 grains. Nickel sulfate 120 grains. Water 2 oz. Saturated solution tartaric acid 1]; oz.

Nitric acid C. P oz.

As an example of a tartrate, a sulfate, a

nitrate and an acid, I may give the followmg:

Cadmium nitrate 60 grains. Sodium tartrate 60 grains. Manganese sulfate 60 grains. \Vater 3 oz. Nitric acid C. P i} oz.

It should be noted that double tartrates, such as the tartrate of potassium-sodium, may be employed in place of combining the necessary single tartrates, and these will produce equally good and in fact identical results that the two single tartrates would if combined in proper molecular proportion. As a matter of fact, the solutions are then identical. Of course, with the use of the single salt, a preponderance of one or the other may be employed at will.

It is to be noted that in the claims where I mention a tartrate, a chlorid, a sulfate or a nitrate, or a combination of any of these without mentioning a particular metal, I include in that term one or more of the salts from the same acid, that is one or more acetates, one or more borates, etc.

Having thus described my invention what I claim and desire to secure by Letters Patent is:

1. In electrolytic etching, an anode carrying a resistant image to'be etched, in combination with an electrolyte comprising one or more of the tartrates of antimony, ammonium, barium, boron, calcium, cadmium, iron, lithium, magnesium, potassium or strontium.

2. In electrolytic etching, an anode carrying a resistant image to be etched, in combination with an electrolyte comprising one or more of the tartrates of antimony, ammonium, barium, boron, calcium, cadmium, iron, lithium, magnesium, potassium or strontium, with an acid.

3. In electrolytic etching, an anode carrying a resistant image to be etched, in combination with an electrolyte com rising one or more of the tartrates of antimony, ammonium, barium, boron, calcium, cadmium, iron, lithium, magnesium, otassium or strontium, with a chlorid an an acid.

4. In electrolytic etchin ,an anode carrying a resistant image to be etc ed, in combination with an electrolyte comprising one or more of the tartrates of antimony, ammonium, barium, boron, calcium, cadmium, iron, lithium, magnesium, with a chlorid, a sulfate and an acid.

5. In electrolytic etching, an anode carrying a resistant image to be etched, in com bination with an electrolyte comprising one or more of the tartrates of antimony, ammonium, barium, boron, calcium, cadmium, iron, lithium, magnesium, potassium or strontium, with a chlorid, a sulfate, a nitrate and an acid.

potassium, or strontium,

.6. In electrolytic etching, an anode carryinga resistant image to be etched, in combination with an electrolyte comprising one 01' more of the tartrates of antimony, am-' -monium, barium, boron, calcium, cadmium, iron, lithium, magnesium, potassium or strontium, with a chromium salt other than .the tartrate and an acid.

7. In electrolytic etching, an anodecarry- 10 ing' a resistantimage to be etched, in commeanest JOSEPH H. WEEKS. 

